This invention relates to thermosetting compositions. In one of its aspects this invention relates to thermosetting compositions based on a mixture of high vinyl diolefin polymers. In another of its aspects, this invention relates to the improvement of physical properties of thermosetting compositions based on a mixture of high vinyl diolefin polymers. In yet another of its aspects, this invention relates to improving the impact strength of thermosetting compositions without loss of other mechanical properties.
Thermosetting compositions based on high vinyl polybutadiene usually exhibit low impact strength. Although the addition of rubbery polymers should help to absorb energy when impacted such an addition also reduces the mechanical properties of such compositions because the rubbery polymers do not cross-link into the matrix.
Improvement of impact strength without loss of other mechanical properties in thermosetting compositions based on high vinyl polybutadiene has, therefore, become of some importance. It has now been discovered that by using a polymer containing styrene-butadiene-high vinyl butadiene, either as the thermoset resin or with another thermoset resin in a typical thermoset composition that such an improvement can be obtained. It has been theorized that in such a composition the cold flow properties and ease of processing are retained by the polystyrene blocks (segments), the impact improved by the polybutadiene blocks (segments), and the mechanical properties retained because the vinyl groups can cross-link into the matrix.
Up until this time thermosetting compositions containing high vinyl-polybutadiene, polyisobutylene, and polybutadiene have been considered as having a good overall balance of physical properties which are an improvement over composition containing high vinyl butadiene-styrene alone or in combination with polyisobutylene. The compositions proposed in the present invention exhibit a superior balance of physical properties to the compositions of the prior art containing cis-polybutadiene and also provide an alternative method for improving the physical properties of high vinyl butadiene-styrene based compositions.
It is, therefore, an object of this invention to provide a thermosetting composition that upon curing exhibits a good balance of physical properties. It is another object of this invention to provide a method for improving the physical properties of thermosetting compositions based on high vinyl butadiene-styrene polymer.
Other aspects, objects and various advantages of this invention will become apparent upon reading this specification and the appended claims.